This invention relates to a method of fabricating a semiconductor device or the like in a high density, thin, and small package.
Semiconductor devices such as IC and LSI are recently used in various electric household appliances and industrial machines. These electric household appliances and industrial machines are promoted in the tendency of being smaller and thinner, or being portable, in order to save resources, save energy or extend the range of applications.
To cope with this portable trend, for semiconductor devices, smaller and thinner packaging is being required. Silicon slices after diffusion process and electrode wiring process are cut into chips in the unit of semiconductor devices, and electrode leads are taken out from the aluminum electrode terminals provided around the chip to the external terminals for the ease of handling, and the chips are packaged to be protected mechanically. Usually, for packaging of these semiconductor devices, DIL, chip carrier, flip chip, tape carrier and other methods are employed, and, for example, the DIL and chip carrier are intended to connect from the electrode terminals of semiconductor device to external terminals one by one sequentially by using ultrathin wires of Au or Al in 25 to 35 .mu.m in diameter. Accordingly, as the number of electrode terminals on the semiconductor device increases, the reliability of connecting positions is lowered, and also the number of external terminals increases as a result at constant intervals, which results in increase of the packaging size.
In the LSI such as I/O connected with the LSI for memory or microcomputer, as the number of functions increases, the number of electrode terminals extremely increases to 60 or even 100 terminals, and the packaging size becomes as large as tens of cubic centimeters for handling a tiny semiconductor device of only tens of cubic millimeters. This was the bottleneck for promotion of downsizing of appliances.
The following methods are known, for example, as the manner of mounting these semiconductor devices at high density, in small size, and in small thickness. In a first method, a semiconductor device is fixed on a wiring substrate having a wiring pattern, and the aluminum electrodes of semiconductor device and wiring pattern are connected by using ultrathin wires of Au or Al. That is, this is a method of mounting a semiconductor device flatly and connecting it with wires, in which the wires stand higher than the semiconductor device and it is difficult to mount thinly, and a region including electrodes of semiconductor device and wiring pattern is needed for connection, and the flat mounting area increases, making it difficult to reduce the size.
In a second method, a metal bump is formed on the aluminum electrode of semiconductor device, and a film lead is joined to it, and the wiring pattern of wiring substrate and said film lead are connected. This method, in order to form a metal bump on the semiconductor device, requires vacuum deposition process, photolithography process, etching process, and plating process, and it not only lowers the yield of semiconductor devices but also raises the packaging cost. Again, same as in the first method, since a region for joining the film lead with the wiring pattern is needed, the flat mounting surface increases, and it is hard to reduce the size.